1. Field of the Invention
Embodiments of the present invention relate generally to the field of data storage and more particularly to transferring data to and from a data storage device.
2. Description of the Related Art
Many popular consumer electronic devices utilize removable data storage devices such as flash memory cards for saving digital content such as photos, music, video or personal data. Several flash memory card standards have been developed, including MultiMediaCard (MMC), Secure Digital Card (SD Card), and Memory Stick, for example. In addition to the removable memory cards that are commonly used, non-removable data storage devices (i.e. “fixed” storage devices) are experiencing increased use. Examples of the fixed data storage devices include a ball grid array multimedia card (MMC BGA), based on the MMC interface, and iNAND, from SanDisk, based on the SD interface. These fixed data storage devices are very similar to their removable data storage device counterparts in how they operate.
The specifications for the removable storage devices originally limited the communication bus between a host system and the removable data storage devices to a single data line (e.g. the ×1 data bus, wherein a data bus can comprise one or more data lines) in order to keep the number of physical connections between the data storage devices and the host to a minimum, wherein such physical connections are referred to herein as contacts, with one example of a contact being a pin. However, as the size of the digital content files stored on the data storage devices has grown so has the data storage capacity of the data storage devices. As a result, the need for faster data transfer between the host and the data storage devices has also increased.
One method for increasing the data transfer rate is increasing the data bus width. For example the data bus width may be increased from ×1 to ×4 or ×8. The ×1, ×4 and ×8 connote the number of data lines. Existing techniques for establishing a wider bus communication include initiating communications between the host and the data storage devices over a default ×1 data bus. The host then queries the data storage devices over the ×1 data bus to extract information about alternative bus configurations supported by the device. If both the host and the data storage device support a wider bus, the host issues a command and the data storage device and the host are re-configured to operate using the wider bus. Unfortunately, this method is somewhat cumbersome when implemented. Specifically, it requires a series of decisions to be made by the host based on the information received from the data storage device. Thus, the host's operating code must branch and each data bus configuration is handled separately. Additionally, switching from the default ×1 bus to a wider bus occurs while the data storage device is active. This requires host interface hardware to be on, allowing for the possibility of a hot switching condition with the memory card.